Cross-component adaptive loop filter

ABSTRACT

A method, computer program, and computer system is provided for video coding. Video data comprising a chroma component and a luma component is received. Luma samples are extracted from the luma component of the received video data. The chroma component is filtered by a cross-component adaptive loop filter (CC-ALF) based on a location of a chroma sample associated with the chroma component, the extracted luma samples, filter weights associated with the extracted luma samples, and an offset value.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation Application of U.S. application Ser. No. 17/022,733, filed on Sep. 16, 2020, which claims priority based on U.S. Provisional Application No. 62/904,644 (filed Sep. 23, 2019), the entirety of which is incorporated herein.

FIELD

This disclosure relates generally to field of data processing, and more particularly to video coding.

BACKGROUND

ITU-T VCEG (Q6/16) and ISO/IEC MPEG (JTC 1/SC 29/WG 11) published the H.265/HEVC (High Efficiency Video Coding) standard in 2013 (version 1) 2014 (version 2) 2015 (version 3) and 2016 (version 4). In 2015, these two standard organizations jointly formed the JVET (Joint Video Exploration Team) to explore the potential of developing the next video coding standard beyond HEVC In October 2017, they issued the Joint Call for Proposals on Video Compression with Capability beyond HEVC (CfP). By Feb. 15, 2018, a total of 22 CfP responses on standard dynamic range (SDR), 12 CfP responses on high dynamic range (HDR), and 12 CfP responses on 360 video categories were submitted, respectively. In April 2018, all received CfP responses were evaluated in the 122 MPEG/10th JVET meeting. As a result of this meeting, JVET formally launched the standardization process of next-generation video coding beyond HEVC. The new standard was named Versatile Video Coding (VVC), and JVET was renamed as Joint Video Expert Team.

SUMMARY

Embodiments relate to a method, system, and computer readable medium for video coding. According to one aspect, a method for video coding is provided. The method may include receiving video data comprising a chroma component and a luma component. Luma samples are extracted from the luma component of the received video data. The chroma component is filtered by a cross-component adaptive loop filter (CC-ALF) based on a location of a chroma sample associated with the chroma component, the extracted luma samples, filter weights associated with the extracted luma samples, and an offset value.

According to another aspect, a computer system for video coding is provided. The computer system may include one or more processors, one or more computer-readable memories, one or more computer-readable tangible storage devices, and program instructions stored on at least one of the one or more storage devices for execution by at least one of the one or more processors via at least one of the one or more memories, whereby the computer system is capable of performing a method. The method may include receiving video data comprising a chroma component and a luma component. Luma samples are extracted from the luma component of the received video data. The chroma component is filtered by a cross-component adaptive loop filter (CC-ALF) based on a location of a chroma sample associated with the chroma component, the extracted luma samples, filter weights associated with the extracted luma samples, and an offset value.

According to yet another aspect, a computer readable medium for video coding is provided. The computer readable medium may include one or more computer-readable storage devices and program instructions stored on at least one of the one or more tangible storage devices, the program instructions executable by a processor. The program instructions are executable by a processor for performing a method that may accordingly include receiving video data comprising a chroma component and a luma component. Luma samples are extracted from the luma component of the received video data. The chroma component is filtered by a cross-component adaptive loop filter (CC-ALF) based on a location of a chroma sample associated with the chroma component, the extracted luma samples, filter weights associated with the extracted luma samples, and an offset value.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages will become apparent from the following detailed description of illustrative embodiments, which is to be read in connection with the accompanying drawings. The various features of the drawings are not to scale as the illustrations are for clarity in facilitating the understanding of one skilled in the art in conjunction with the detailed description. In the drawings:

FIG. 1 illustrates a networked computer environment according to at least one embodiment;

FIG. 2 is a block diagram of a cross-component adaptive loop filter (CC-ALF) for video coding, according to at least one embodiment;

FIG. 3 is an operational flowchart illustrating the steps carried out by a program for video coding, according to at least one embodiment;

FIG. 4 is a block diagram of internal and external components of computers and servers depicted in FIG. 1 according to at least one embodiment;

FIG. 5 is a block diagram of an illustrative cloud computing environment including the computer system depicted in FIG. 1 , according to at least one embodiment; and

FIG. 6 is a block diagram of functional layers of the illustrative cloud computing environment of FIG. 5 , according to at least one embodiment.

DETAILED DESCRIPTION

Detailed embodiments of the claimed structures and methods are disclosed herein; however, it can be understood that the disclosed embodiments are merely illustrative of the claimed structures and methods that may be embodied in various forms. Those structures and methods may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope to those skilled in the art. In the description, details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the presented embodiments.

Embodiments relate generally to the field of data processing, and more particularly to media processing. The following described exemplary embodiments provide a system, method and computer program to, among other things, refine a chroma component of video data using a luma component of the video data. Therefore, some embodiments have the capacity to improve the field of computing by allowing for improved encoding and decoding through filtering of luma samples used for encoding and decoding.

As previously described, ITU-T VCEG (Q6/16) and ISO/IEC MPEG (JTC 1/SC 29/WG 11) published the H.265/HEVC (High Efficiency Video Coding) standard in 2013 (version 1) 2014 (version 2) 2015 (version 3) and 2016 (version 4). In 2015, these two standard organizations jointly formed the JVET (Joint Video Exploration Team) to explore the potential of developing the next video coding standard beyond HEVC In October 2017, they issued the Joint Call for Proposals on Video Compression with Capability beyond HEVC (CfP). By Feb. 15, 2018, a total of 22 CfP responses on standard dynamic range (SDR), 12 CfP responses on high dynamic range (HDR), and 12 CfP responses on 360 video categories were submitted, respectively. In April 2018, all received CfP responses were evaluated in the 122 MPEG/10th JVET meeting. As a result of this meeting, JVET formally launched the standardization process of next-generation video coding beyond HEVC. The new standard was named Versatile Video Coding (VVC), and JVET was renamed as Joint Video Expert Team. In VVC, a cross-component adaptive loop filter (CC-ALF) may make use of luma sample values from video data to refine a chroma component of the video data. However, when neighboring luma samples are too different from the current luma sample value, it may cause negative filtering effect toward the chroma sample to be filtered. It may be advantageous, therefore, to filter the luma samples to prevent the negative filtering effects.

Aspects are described herein with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer readable media according to the various embodiments. It will be understood that each block of the flowchart illustrations and/or block diagrams, and combinations of blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer readable program instructions.

The following described exemplary embodiments provide a system, method and computer program that allows for refinement of a chroma component of video data using a luma component of the video data. Referring now to FIG. 1 , a functional block diagram of a networked computer environment illustrating a media processing system 100 (hereinafter “system”) for video coding. It should be appreciated that FIG. 1 provides only an illustration of one implementation and does not imply any limitations with regard to the environments in which different embodiments may be implemented. Many modifications to the depicted environments may be made based on design and implementation requirements.

The system 100 may include a computer 102 and a server computer 114. The computer 102 may communicate with the server computer 114 via a communication network 110 (hereinafter “network”). The computer 102 may include a processor 104 and a software program 108 that is stored on a data storage device 106 and is enabled to interface with a user and communicate with the server computer 114. As will be discussed below with reference to FIG. 4 the computer 102 may include internal components 800A and external components 900A, respectively, and the server computer 114 may include internal components 800B and external components 900B, respectively. The computer 102 may be, for example, a mobile device, a telephone, a personal digital assistant, a netbook, a laptop computer, a tablet computer, a desktop computer, or any type of computing devices capable of running a program, accessing a network, and accessing a database.

The server computer 114 may also operate in a cloud computing service model, such as Software as a Service (SaaS), Platform as a Service (PaaS), or Infrastructure as a Service (IaaS), as discussed below with respect to FIGS. 5 and 6 . The server computer 114 may also be located in a cloud computing deployment model, such as a private cloud, community cloud, public cloud, or hybrid cloud.

The server computer 114, which may be used for video coding is enabled to run an CC-ALF Program 116 (hereinafter “program”) that may interact with a database 112. The CC-ALF Program method is explained in more detail below with respect to FIG. 3 . In one embodiment, the computer 102 may operate as an input device including a user interface while the program 116 may run primarily on server computer 114. In an alternative embodiment, the program 116 may run primarily on one or more computers 102 while the server computer 114 may be used for processing and storage of data used by the program 116. It should be noted that the program 116 may be a standalone program or may be integrated into a larger CC-ALF program.

It should be noted, however, that processing for the program 116 may, in some instances be shared amongst the computers 102 and the server computers 114 in any ratio. In another embodiment, the program 116 may operate on more than one computer, server computer, or some combination of computers and server computers, for example, a plurality of computers 102 communicating across the network 110 with a single server computer 114. In another embodiment, for example, the program 116 may operate on a plurality of server computers 114 communicating across the network 110 with a plurality of client computers. Alternatively, the program may operate on a network server communicating across the network with a server and a plurality of client computers.

The network 110 may include wired connections, wireless connections, fiber optic connections, or some combination thereof. In general, the network 110 can be any combination of connections and protocols that will support communications between the computer 102 and the server computer 114. The network 110 may include various types of networks, such as, for example, a local area network (LAN), a wide area network (WAN) such as the Internet, a telecommunication network such as the Public Switched Telephone Network (PSTN), a wireless network, a public switched network, a satellite network, a cellular network (e.g., a fifth generation (5G) network, a long-term evolution (LTE) network, a third generation (3G) network, a code division multiple access (CDMA) network, etc.), a public land mobile network (PLMN), a metropolitan area network (MAN), a private network, an ad hoc network, an intranet, a fiber optic-based network, or the like, and/or a combination of these or other types of networks.

The number and arrangement of devices and networks shown in FIG. 1 are provided as an example. In practice, there may be additional devices and/or networks, fewer devices and/or networks, different devices and/or networks, or differently arranged devices and/or networks than those shown in FIG. 1 . Furthermore, two or more devices shown in FIG. 1 may be implemented within a single device, or a single device shown in FIG. 1 may be implemented as multiple, distributed devices. Additionally, or alternatively, a set of devices (e.g., one or more devices) of system 100 may perform one or more functions described as being performed by another set of devices of system 100.

Referring now to FIG. 2 , a block diagram of an exemplary cross-component adaptive loop filter (CC-ALF filter) 200 with block-based filter adaption is depicted. The CC-ALF filter 200 may include a chroma component 202 and a luma component 204. For the luma component 204, one filter among twenty-five filters may be selected for each 4×4 block, based on the direction and activity of local gradients. Two diamond filter shapes may be used. A 7-by-7 diamond shape 202 may be applied for luma components and a 5-by-5 diamond shape may be applied for chroma components.

The CC-ALF filter 200 may make use of luma sample values to refine each chroma component by applying a linear, diamond shaped filter to the luma channel for each chroma component. The filter coefficients are transmitted may be scaled by a factor of 2¹⁰ and rounded for fixed point representation. The application of the filters may be controlled on a variable block size and signalled by a context-coded flag received for each block of samples. The block size along with an CC-ALF enabling flag may be received at the slice-level for each chroma component.

For the chroma components in a picture, a single set of ALF coefficients C0-C6 may is applied for the chroma component 202.

For the luma component 204, each 4-by-4 block may be categorized into one of twenty-five classes. A classification index C may be derived based on its directionality D and a quantized value of activity Â, such that C=5D+Â. To calculate D and Â, gradients of the horizontal, vertical and two diagonal direction may be calculated using 1-D Laplacian:

$\mspace{76mu}{{g_{v} = {\sum\limits_{k = {i - 2}}^{i + 3}\;{\sum\limits_{l = {j - 2}}^{j + 3}\; V_{k,l}}}},{V_{k,l} = {{{2{R\left( {k,l} \right)}} - {R\left( {k,{l - 1}} \right)} - {R\left( {k,{l + 1}} \right)}}}}}$ $\mspace{76mu}{{g_{h} = {\sum\limits_{k = {i - 2}}^{i + 3}\;{\sum\limits_{l = {j - 2}}^{j + 3}\; H_{k,l}}}},{H_{k,l} = {{{2{R\left( {k,l} \right)}} - {R\left( {{k - 1},l} \right)} - {R\left( {{k + 1},l} \right)}}}}}$ ${g_{d\; 1} = {\sum\limits_{k = {i - 2}}^{i + 3}\;{\sum\limits_{l = {j - 2}}^{j + 3}\;{D\; 1_{k,l}}}}},{{D\; 1_{k,l}} = {{{2{R\left( {k,l} \right)}} - {R\left( {{k - 1},{l - 1}} \right)} - {R\left( {{k + 1},{l + 1}} \right)}}}}$ ${g_{d\; 2} = {\sum\limits_{k = {i - 2}}^{i + 3}\;{\sum\limits_{l = {j - 2}}^{j + 3}\;{D\; 2_{k,l}}}}},{{D\; 2_{k,l}} = {{{2{R\left( {k,l} \right)}} - {R\left( {{k - 1},{l + 1}} \right)} - {R\left( {{k + 1},{l - 1}} \right)}}}},$ where indices i and j may refer to the coordinates of the upper left sample within the 4×4 block and R(l,j) may indicate a reconstructed sample at coordinate (l,j). To reduce the complexity of block classification, the subsampled 1-D Laplacian calculation is applied. The same subsampled positions may be used for gradient calculation of all directions.

Maximum and minimum D values of the gradients of horizontal and vertical directions may be set as: g _(h,v) ^(max)=max(g _(h) ,g _(v)),g _(h,v) ^(min)=min(g _(h) ,g _(v)). The maximum and minimum values of the gradient of two diagonal directions may be set as: g _(d0,d1) ^(max)=max(g _(d0) ,g _(d1)),g _(d0,d1) ^(min)=min(g _(d0) ,g _(d1))

To derive the value of the directionality D, the maximum and minimum values may be compared against each other and with two thresholds t₁ and t₂. If both g_(h,v) ^(max)≤t₁·g_(h,v) ^(min) and g_(d0,d1) ^(max)≤t₁·g_(d0,d1) ^(min) are true, D is set to 0. If g_(h,v) ^(max)/g_(h,v) ^(min)>g_(d0,d1) ^(max)/g_(d0,d1) ^(min), then if g_(h,v) ^(max)/g_(h,v) ^(min)>t₂·g_(h,v) ^(min), D may be set to 2; otherwise D may be set to 1. If g_(h,v) ^(max)/g_(h,v) ^(min)≤g_(d0,d1) ^(max)/g_(d0,d1) ^(min), then if g_(d0,d1) ^(max)>t₂·g_(d0,d1) ^(min), D may be set to 4; otherwise D may be set to 3.

The activity value may be calculated as:

$A = {\sum\limits_{k = {i - 2}}^{i + 3}\;{\sum\limits_{l = {j - 2}}^{j + 3}{\left( {V_{k,l} + H_{k,l}} \right).}}}$ A may be further quantized to the range of 0 to 4, inclusively. The quantized value may be denoted as Â.

At a decoder side, when ALF may be enabled, each sample R(i,j) within the CU may be filtered, resulting in sample value

${{R^{\prime}\left( {i,j} \right)} = {{R\left( {i,j} \right)} + \left( {\left( {{\sum\limits_{k \neq 0}{\sum\limits_{l \neq 0}{{f\left( {k,l} \right)} \times {K\left( {{{R\left( {{i + k},{j + l}} \right)} - {R\left( {i,j} \right)}},{c\left( {k,l} \right)}} \right)}}}} + 64} \right)\mspace{25mu}\text{>>}\mspace{14mu} 7} \right)}}\;$ where f(k,l) may denote the decoded filter coefficients, K(x,y) may be a clipping function and c(k,l) may denote decoded clipping parameters. The variables k and l may vary between

${{- \frac{L}{2}}\mspace{14mu}{and}\mspace{14mu}\frac{L}{2}},$ where L may denote the filter length. The clipping function K(x,y)=min(y,max(−y,x)) may correspond to the function Clip3 (−y,y,x). By incorporating this clipping function, the loop filtering method becomes a non-linear process, known as Non-Linear ALF.

According to one or more embodiments, the CC-ALF filtering process may be denoted by O(x,y)=Σw(i,j)I_(L)(x+i,y+j) and I_(C)′(x,y)=I_(C)(x,y)+O(x,y), where (x,y) may indicate a location of a chroma sample to be filtered, I_(L)(x+i,y+j) may be input luma samples, w(i,j) may denote filter weights associated with each input sample, O(x,y) may be an offset computed by luma channel, and I_(C)(x,y) and I_(C)′(x,y) may be the chroma samples before and after applying CC-ALF filtering, respectively.

According to one or more embodiments, a non-linear filter in CC-ALF may be applied to constrain the strength of filtering in CC-ALF. The filtering process may be denoted by O(x,y)=Σw(i,j)ƒ(I_(L)(x+i,y+j), I_(L)(x,y), c(i,j)), where ƒ(*) may be a non-linear function taking the input luma sample I_(L)(x+i,y+j) located at (x+i,y+j), and current luma sample I_(L)(x,y) as inputs. In one or more embodiments, ƒ(a,b,δ)=min(b+c,max(a,b−δ)) may be the clipping function, and c(i,j) may be clipping values applied on the samples located at (x+i, y+j). In one or more embodiments, ƒ(a,b,δ) may be a high-pass filter such as:

${f\left( {a,b,\delta} \right)} = \left\{ {\begin{matrix} 0 & {{{if}\mspace{14mu} a} < {b - {\delta\mspace{14mu}{or}\mspace{14mu} a}} > {b + \delta}} \\ a & {otherwise} \end{matrix}.} \right.$ In one or more embodiments, ƒ(a,b, δ₁,δ₂) may be a band-pass filter such as:

${f\left( {a,b,\delta_{1},\delta_{2}} \right)} = \left\{ {\begin{matrix} a & {{{{if}\mspace{14mu} b} - \delta_{1}} < a < {b - {\delta_{2}\mspace{14mu}{or}\mspace{14mu} b} + \delta_{2}} < a < {b + \delta_{1}}} \\ 0 & {otherwise} \end{matrix}.} \right.$ The clipping value δ(i,j) may be signaled in high level syntax, including but not limited to Slice Header, PPS (Picture Parameter Set), SPS (Sequence Parameter Set), and/or APS. The clipping value δ(i,j) may be derived directly. For example, it may be derived based on the difference between current sample and its neighboring samples. The clipping value δ(i,j) may alternatively be derived based on previously coded information, including, but not limited to reconstructed values, coding mode, block partitioning size.

According to one or more embodiments, the CC-ALF filtering process may be denoted by O(x,y)=Σƒ(I_(L)(x+i,y+j), I_(L)(x,y))I_(L)(x+i,y+j), where ƒ(I_(L)(x+i,y+j), I_(L)(x,y)) may derive filter weights. In one or more embodiments, the filter weights may be derived based on the difference between current sample and its neighboring samples. In one or more embodiments, the difference between the current sample and its neighboring samples may be d=I_(L)(x+i,y+j)−I_(L)(x,y). ƒ(I_(L)(x+i,y+j), I_(L)(x,y)) may a Gaussian function of d, such that

${{f(d)} = e^{({- \frac{d^{2}}{2\sigma^{2}}})}},$ where σ may be a given controlling parameter specifying the filtering strength. In one or more embodiments, the outputs of function ƒ(*) for different input may be pre-defined. For example, the pre-defined output values may be be specified in HLS or stored as a constant LUT.

According to one or more embodiments, instead of using the luma samples filtered by sample-adaptive offset (SAO) as inputs as used in the original CC-ALF design, a different input source of CC-ALF may be used. The output of CC-ALF may be applied on Cb/Cr after chroma ALF filtering. In one or more embodiments, the input luma samples of CC-ALF may be be samples before luma SAO filtering and after luma deblocking filtering. In one or more embodiments, the input of CC-ALF may be reconstructed luma samples before applying luma deblocking filtering. In one or more embodiments, the input of CC-ALF may be luma samples after applying luma ALF filtering.

According to one or more embodiments, instead of using luma samples as input of CC-ALF and the output is applied on the reconstructed chroma samples, chroma samples may be used as input of CC-ALF and the output may be applied on the luma samples. Chroma samples can refer to either Cb samples or Cr samples, or a combination of Cb and Cr samples. In one or more embodiments, the input chroma samples of CC-ALF may be chroma samples before applying chroma ALF filtering and after chroma SAO filtering. In one or more embodiments, the input chroma samples of CC-ALF may be samples before chroma SAO filtering and after chroma deblocking filtering. In one or more embodiments, the input of CC-ALF may be reconstructed chroma samples before applying chroma deblocking filtering. In one or more embodiments, the input of CC-ALF may be chroma samples after applying chroma ALF filtering.

According to one or more embodiments, Cb samples may be used as input of CC-ALF and the output may be applied on the Cr samples. Alternatively, Cr samples may be used as input of CC-ALF and the output may be applied on the Cb samples. In one or more embodiments, the input Cb (or Cr) samples of CC-ALF may be Cb (or Cr) samples before applying Cb (or Cr) ALF filtering and after Cb (or Cr) SAO filtering. In one or more embodiments, the input Cb (or Cr) samples of CC-ALF may be samples before Cb (or Cr) SAO filtering and after Cb (or Cr) deblocking. In one or more embodiments, the input of CC-ALF may be reconstructed luma samples before applying luma deblocking filtering. In one or more embodiments, the input of CC-ALF may be Cb (or Cr) samples after applying Cb (or Cr) ALF filtering.

According to one or more embodiments, instead of processing luma ALF filtering before chroma ALF filtering, chroma ALF filtering may be processed before luma ALF filtering. The processing order of loop filtering of different color components may be pre-defined. Alternatively, the processing order of loop filtering of different color components may be signaled by an individual flag or index.

Referring now to FIG. 3 , an operational flowchart 300 illustrating the steps carried out by a program for video coding is depicted. FIG. 3 may be described with the aid of FIGS. 1 and 2 . As previously described, the CC-ALF Program 116 (FIG. 1 ) may constrain CC-ALF coefficients.

At 302, video data comprising a chroma component and a luma component is received. The video data may include multiple frames that may each include a chroma component and a luma component. In operation, the CC-ALF Program 116 (FIG. 1 ) on the server computer 114 (FIG. 1 ) may receive video data from the computer 102 (FIG. 1 ) over the communication network 110 (FIG. 1 ) or may retrieve the video data 204 from the database 112 (FIG. 1 ).

At 304, luma samples are extracted from the luma component of the received video data. The luma samples may be four pixels by four pixel in size. The luma samples may be used to refine the chroma component. In operation, the CC-ALF Program 116 (FIG. 1 ) may extract luma samples from the received video data.

At 306, the chroma component is filtered by a cross-component adaptive loop filter (CC-ALF) based on a location of a chroma sample associated with the chroma component, the extracted luma samples, filter weights associated with the extracted luma samples, and an offset value. In operation, the CC-ALF Program 116 (FIG. 1 ) use the coefficients C0-C6 of the chroma component 202 (FIG. 2 ) and the coefficients C0-C12 of the luma component 204 (FIG. 2 ) of the CC-ALF filter 200 (FIG. 2 ) based on the luma samples to filter the chroma component of the received video data. The CC-ALF Program 116 may encode and/or decode video data based on the filtered chroma component

It may be appreciated that FIG. 3 provides only an illustration of one implementation and does not imply any limitations with regard to how different embodiments may be implemented. Many modifications to the depicted environments may be made based on design and implementation requirements.

FIG. 4 is a block diagram 400 of internal and external components of computers depicted in FIG. 1 in accordance with an illustrative embodiment. It should be appreciated that FIG. 4 provides only an illustration of one implementation and does not imply any limitations with regard to the environments in which different embodiments may be implemented. Many modifications to the depicted environments may be made based on design and implementation requirements.

Computer 102 (FIG. 1 ) and server computer 114 (FIG. 1 ) may include respective sets of internal components 800A,B and external components 900A,B illustrated in FIG. 4 . Each of the sets of internal components 800 include one or more processors 820, one or more computer-readable RAMs 822 and one or more computer-readable ROMs 824 on one or more buses 826, one or more operating systems 828, and one or more computer-readable tangible storage devices 830.

Processor 820 is implemented in hardware, firmware, or a combination of hardware and software. Processor 820 is a central processing unit (CPU), a graphics processing unit (GPU), an accelerated processing unit (APU), a microprocessor, a microcontroller, a digital signal processor (DSP), a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or another type of processing component. In some implementations, processor 820 includes one or more processors capable of being programmed to perform a function. Bus 826 includes a component that permits communication among the internal components 800A,B.

The one or more operating systems 828, the software program 108 (FIG. 1 ) and the CC-ALF Program 116 (FIG. 1 ) on server computer 114 (FIG. 1 ) are stored on one or more of the respective computer-readable tangible storage devices 830 for execution by one or more of the respective processors 820 via one or more of the respective RAMs 822 (which typically include cache memory). In the embodiment illustrated in FIG. 4 , each of the computer-readable tangible storage devices 830 is a magnetic disk storage device of an internal hard drive. Alternatively, each of the computer-readable tangible storage devices 830 is a semiconductor storage device such as ROM 824, EPROM, flash memory, an optical disk, a magneto-optic disk, a solid state disk, a compact disc (CD), a digital versatile disc (DVD), a floppy disk, a cartridge, a magnetic tape, and/or another type of non-transitory computer-readable tangible storage device that can store a computer program and digital information.

Each set of internal components 800A,B also includes a R/W drive or interface 832 to read from and write to one or more portable computer-readable tangible storage devices 936 such as a CD-ROM, DVD, memory stick, magnetic tape, magnetic disk, optical disk or semiconductor storage device. A software program, such as the software program 108 (FIG. 1 ) and the CC-ALF Program 116 (FIG. 1 ) can be stored on one or more of the respective portable computer-readable tangible storage devices 936, read via the respective R/W drive or interface 832 and loaded into the respective hard drive 830.

Each set of internal components 800A,B also includes network adapters or interfaces 836 such as a TCP/IP adapter cards; wireless Wi-Fi interface cards; or 3G, 4G, or 5G wireless interface cards or other wired or wireless communication links. The software program 108 (FIG. 1 ) and the CC-ALF Program 116 (FIG. 1 ) on the server computer 114 (FIG. 1 ) can be downloaded to the computer 102 (FIG. 1 ) and server computer 114 from an external computer via a network (for example, the Internet, a local area network or other, wide area network) and respective network adapters or interfaces 836. From the network adapters or interfaces 836, the software program 108 and the CC-ALF Program 116 on the server computer 114 are loaded into the respective hard drive 830. The network may comprise copper wires, optical fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers.

Each of the sets of external components 900A,B can include a computer display monitor 920, a keyboard 930, and a computer mouse 934. External components 900A,B can also include touch screens, virtual keyboards, touch pads, pointing devices, and other human interface devices. Each of the sets of internal components 800A,B also includes device drivers 840 to interface to computer display monitor 920, keyboard 930 and computer mouse 934. The device drivers 840, R/W drive or interface 832 and network adapter or interface 836 comprise hardware and software (stored in storage device 830 and/or ROM 824).

It is understood in advance that although this disclosure includes a detailed description on cloud computing, implementation of the teachings recited herein are not limited to a cloud computing environment. Rather, some embodiments are capable of being implemented in conjunction with any other type of computing environment now known or later developed.

Cloud computing is a model of service delivery for enabling convenient, on-demand network access to a shared pool of configurable computing resources (e.g. networks, network bandwidth, servers, processing, memory, storage, applications, virtual machines, and services) that can be rapidly provisioned and released with minimal management effort or interaction with a provider of the service. This cloud model may include at least five characteristics, at least three service models, and at least four deployment models.

Characteristics are as follows:

On-demand self-service: a cloud consumer can unilaterally provision computing capabilities, such as server time and network storage, as needed automatically without requiring human interaction with the service's provider.

Broad network access: capabilities are available over a network and accessed through standard mechanisms that promote use by heterogeneous thin or thick client platforms (e.g., mobile phones, laptops, and PDAs).

Resource pooling: the provider's computing resources are pooled to serve multiple consumers using a multi-tenant model, with different physical and virtual resources dynamically assigned and reassigned according to demand. There is a sense of location independence in that the consumer generally has no control or knowledge over the exact location of the provided resources but may be able to specify location at a higher level of abstraction (e.g., country, state, or datacenter).

Rapid elasticity: capabilities can be rapidly and elastically provisioned, in some cases automatically, to quickly scale out and rapidly released to quickly scale in. To the consumer, the capabilities available for provisioning often appear to be unlimited and can be purchased in any quantity at any time.

Measured service: cloud systems automatically control and optimize resource use by leveraging a metering capability at some level of abstraction appropriate to the type of service (e.g., storage, processing, bandwidth, and active user accounts). Resource usage can be monitored, controlled, and reported providing transparency for both the provider and consumer of the utilized service.

Service Models are as follows:

Software as a Service (SaaS): the capability provided to the consumer is to use the provider's applications running on a cloud infrastructure. The applications are accessible from various client devices through a thin client interface such as a web browser (e.g., web-based e-mail). The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings.

Platform as a Service (PaaS): the capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages and tools supported by the provider. The consumer does not manage or control the underlying cloud infrastructure including networks, servers, operating systems, or storage, but has control over the deployed applications and possibly application hosting environment configurations.

Infrastructure as a Service (laaS): the capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, deployed applications, and possibly limited control of select networking components (e.g., host firewalls).

Deployment Models are as follows:

Private cloud: the cloud infrastructure is operated solely for an organization. It may be managed by the organization or a third party and may exist on-premises or off-premises.

Community cloud: the cloud infrastructure is shared by several organizations and supports a specific community that has shared concerns (e.g., mission, security requirements, policy, and compliance considerations). It may be managed by the organizations or a third party and may exist on-premises or off-premises.

Public cloud: the cloud infrastructure is made available to the general public or a large industry group and is owned by an organization selling cloud services.

Hybrid cloud: the cloud infrastructure is a composition of two or more clouds (private, community, or public) that remain unique entities but are bound together by standardized or proprietary technology that enables data and application portability (e.g., cloud bursting for load-balancing between clouds).

A cloud computing environment is service oriented with a focus on statelessness, low coupling, modularity, and semantic interoperability. At the heart of cloud computing is an infrastructure comprising a network of interconnected nodes.

Referring to FIG. 5 , illustrative cloud computing environment 500 is depicted. As shown, cloud computing environment 500 comprises one or more cloud computing nodes 10 with which local computing devices used by cloud consumers, such as, for example, personal digital assistant (PDA) or cellular telephone 54A, desktop computer 54B, laptop computer 54C, and/or automobile computer system 54N may communicate. Cloud computing nodes 10 may communicate with one another. They may be grouped (not shown) physically or virtually, in one or more networks, such as Private, Community, Public, or Hybrid clouds as described hereinabove, or a combination thereof. This allows cloud computing environment 500 to offer infrastructure, platforms and/or software as services for which a cloud consumer does not need to maintain resources on a local computing device. It is understood that the types of computing devices 54A-N shown in FIG. 5 are intended to be illustrative only and that cloud computing nodes 10 and cloud computing environment 500 can communicate with any type of computerized device over any type of network and/or network addressable connection (e.g., using a web browser).

Referring to FIG. 6 , a set of functional abstraction layers 600 provided by cloud computing environment 500 (FIG. 5 ) is shown. It should be understood in advance that the components, layers, and functions shown in FIG. 6 are intended to be illustrative only and embodiments are not limited thereto. As depicted, the following layers and corresponding functions are provided:

Hardware and software layer 60 includes hardware and software components. Examples of hardware components include: mainframes 61; RISC (Reduced Instruction Set Computer) architecture based servers 62; servers 63; blade servers 64; storage devices 65; and networks and networking components 66. In some embodiments, software components include network application server software 67 and database software 68.

Virtualization layer 70 provides an abstraction layer from which the following examples of virtual entities may be provided: virtual servers 71; virtual storage 72; virtual networks 73, including virtual private networks; virtual applications and operating systems 74; and virtual clients 75.

In one example, management layer 80 may provide the functions described below. Resource provisioning 81 provides dynamic procurement of computing resources and other resources that are utilized to perform tasks within the cloud computing environment. Metering and Pricing 82 provide cost tracking as resources are utilized within the cloud computing environment, and billing or invoicing for consumption of these resources. In one example, these resources may comprise application software licenses. Security provides identity verification for cloud consumers and tasks, as well as protection for data and other resources. User portal 83 provides access to the cloud computing environment for consumers and system administrators. Service level management 84 provides cloud computing resource allocation and management such that required service levels are met. Service Level Agreement (SLA) planning and fulfillment 85 provide pre-arrangement for, and procurement of, cloud computing resources for which a future requirement is anticipated in accordance with an SLA.

Workloads layer 90 provides examples of functionality for which the cloud computing environment may be utilized. Examples of workloads and functions which may be provided from this layer include: mapping and navigation 91; software development and lifecycle management 92; virtual classroom education delivery 93; data analytics processing 94; transaction processing 95; and Cross-Component Adaptive Loop Filtering (CC-ALF) 96. CC-ALF 96 may allow for encoding and decoding of video data with constrained filtering coefficients to limit the dynamic range of the video data.

Some embodiments may relate to a system, a method, and/or a computer readable medium at any possible technical detail level of integration. The computer readable medium may include a computer-readable non-transitory storage medium (or media) having computer readable program instructions thereon for causing a processor to carry out operations.

The computer readable storage medium can be a tangible device that can retain and store instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but is not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any suitable combination of the foregoing. A non-exhaustive list of more specific examples of the computer readable storage medium includes the following: a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanically encoded device such as punch-cards or raised structures in a groove having instructions recorded thereon, and any suitable combination of the foregoing. A computer readable storage medium, as used herein, is not to be construed as being transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide or other transmission media (e.g., light pulses passing through a fiber-optic cable), or electrical signals transmitted through a wire.

Computer readable program instructions described herein can be downloaded to respective computing/processing devices from a computer readable storage medium or to an external computer or external storage device via a network, for example, the Internet, a local area network, a wide area network and/or a wireless network. The network may comprise copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and/or edge servers. A network adapter card or network interface in each computing/processing device receives computer readable program instructions from the network and forwards the computer readable program instructions for storage in a computer readable storage medium within the respective computing/processing device.

Computer readable program code/instructions for carrying out operations may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, configuration data for integrated circuitry, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as Smalltalk, C++, or the like, and procedural programming languages, such as the “C” programming language or similar programming languages. The computer readable program instructions may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). In some embodiments, electronic circuitry including, for example, programmable logic circuitry, field-programmable gate arrays (FPGA), or programmable logic arrays (PLA) may execute the computer readable program instructions by utilizing state information of the computer readable program instructions to personalize the electronic circuitry, in order to perform aspects or operations.

These computer readable program instructions may be provided to a processor of a general purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These computer readable program instructions may also be stored in a computer readable storage medium that can direct a computer, a programmable data processing apparatus, and/or other devices to function in a particular manner, such that the computer readable storage medium having instructions stored therein comprises an article of manufacture including instructions which implement aspects of the function/act specified in the flowchart and/or block diagram block or blocks.

The computer readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device to cause a series of operational steps to be performed on the computer, other programmable apparatus or other device to produce a computer implemented process, such that the instructions which execute on the computer, other programmable apparatus, or other device implement the functions/acts specified in the flowchart and/or block diagram block or blocks.

The flowchart and block diagrams in the Figures illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer readable media according to various embodiments. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of instructions, which comprises one or more executable instructions for implementing the specified logical function(s). The method, computer system, and computer readable medium may include additional blocks, fewer blocks, different blocks, or differently arranged blocks than those depicted in the Figures. In some alternative implementations, the functions noted in the blocks may occur out of the order noted in the Figures. For example, two blocks shown in succession may, in fact, be executed concurrently or substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts or carry out combinations of special purpose hardware and computer instructions.

It will be apparent that systems and/or methods, described herein, may be implemented in different forms of hardware, firmware, or a combination of hardware and software. The actual specialized control hardware or software code used to implement these systems and/or methods is not limiting of the implementations. Thus, the operation and behavior of the systems and/or methods were described herein without reference to specific software code—it being understood that software and hardware may be designed to implement the systems and/or methods based on the description herein.

No element, act, or instruction used herein should be construed as critical or essential unless explicitly described as such. Also, as used herein, the articles “a” and “an” are intended to include one or more items, and may be used interchangeably with “one or more.” Furthermore, as used herein, the term “set” is intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, etc.), and may be used interchangeably with “one or more.” Where only one item is intended, the term “one” or similar language is used. Also, as used herein, the terms “has,” “have,” “having,” or the like are intended to be open-ended terms. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.

The descriptions of the various aspects and embodiments have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Even though combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of possible implementations. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of possible implementations includes each dependent claim in combination with every other claim in the claim set. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein. 

What is claimed is:
 1. A method of coding video data, executable by a processor, comprising: extracting luma samples from a luma component of video data; and filtering a chroma component of the video data by a cross-component adaptive loop filter (CC-ALF) based on a location of a chroma sample associated with the chroma component, the extracted luma samples, filter weights associated with the extracted luma samples, and an offset value, wherein the chroma sample includes at least one from among red-difference chroma samples, blue-difference chroma samples, and a combination of red-difference chroma samples and blue-difference chroma samples.
 2. The method of claim 1, wherein a non-linear filter component is applied to the CC-ALF to constrain a filter strength associated with the CC-ALF.
 3. The method of claim 2, wherein the non-linear filter component comprises at least one from among a clipping function, a high-pass filter, and a band-pass filter.
 4. The method of claim 1, wherein the filter weights are derived based on a difference between a current luma sample from among the extracted luma samples and one or more neighboring samples associated with the current luma sample.
 5. The method of claim 1, wherein a luma deblocking filter process is applied to the extracted luma samples and a sample-adaptive offset filtering process has not been applied.
 6. The method of claim 1, wherein an input of CC-ALF is a reconstructed luma sample to which luma deblocking filtering has not been applied.
 7. The method of claim 1, wherein, one or more chroma samples associated with the chroma component are used as an input to the CC-ALF and one or more luma samples are received as an output.
 8. The method of claim 1, wherein the CC-ALF refines the chroma component based on applying a linear filter to the luma component that is controlled on a variable block size and signalled by a context-coded flag received for each block of samples.
 9. The method of claim 1, wherein the CC-ALF processes the luma component prior to processing the chroma component.
 10. The method of claim 1, further comprising encoding or decoding the video data based on the filtered chroma component.
 11. A computer system for video coding, the computer system comprising: one or more computer-readable non-transitory storage media configured to store computer program code; and one or more computer processors configured to access said computer program code and operate as instructed by said computer program code, said computer program code including: extracting code configured to cause the one or more computer processors to extract luma samples from a luma component of video data; and filtering code configured to cause the one or more computer processors to filter a chroma component of the video data by a cross-component adaptive loop filter (CC-ALF) based on a location of a chroma sample associated with the chroma component, the extracted luma samples, filter weights associated with the extracted luma samples, and an offset value, wherein the chroma sample includes at least one from among red-difference chroma samples, blue-difference chroma samples, and a combination of red-difference chroma samples and blue-difference chroma samples.
 12. The computer system of claim 11, wherein a non-linear filter component is applied to the CC-ALF to constrain a filter strength associated with the CC-ALF.
 13. The computer system of claim 12, wherein the non-linear filter component comprises at least one from among a clipping function, a high-pass filter, and a band-pass filter.
 14. The computer system of claim 11, wherein the filter weights are derived based on a difference between a current luma sample from among the extracted luma samples and one or more neighboring samples associated with the current luma sample.
 15. The computer system of claim 11, wherein a luma deblocking filter process is applied to the extracted luma samples and a sample-adaptive offset filtering process has not been applied.
 16. The computer system of claim 11, wherein an input of CC-ALF is a reconstructed luma sample to which luma deblocking filtering has not been applied.
 17. The computer system of claim 11, wherein, one or more chroma samples associated with the chroma component are used as an input to the CC-ALF and one or more luma samples are received as an output.
 18. The method of claim 1, wherein the CC-ALF refines the chroma component based on applying a linear filter to the luma component that is controlled on a variable block size and signalled by a context-coded flag received for each block of samples.
 19. The computer system of claim 11, further comprising encoding and decoding code configured to cause the one or more computer processors to encode or decode the video data based on the filtered chroma component.
 20. A non-transitory computer readable medium having stored thereon a computer program for video coding, the computer program configured to cause one or more computer processors to: extract luma samples from a luma component of video data; and filter a chroma component of the video data by a cross-component adaptive loop filter (CC-ALF) based on a location of a chroma sample associated with the chroma component, the extracted luma samples, filter weights associated with the extracted luma samples, and an offset value, wherein the chroma sample includes at least one from among red-difference chroma samples, blue-difference chroma samples, and a combination of red-difference chroma samples and blue-difference chroma samples. 